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Most people now accept that weather can affect mood state and for some people can lead to extreme depression in the form of Seasonal Affective Disorder. There also seems to be some evidence that weather can affect people’s sex lives. Being too hot or too cold is likely to lessen the desire to engage in sexual behaviour. Most academic research appears to indicate that sex drives are higher in spring and summer. One of the reasons given for this is that during spring and summer, there is more sun, and that a particular hormone – Melanocyte Stimulating Hormone (MSH) – stimulates sex, particularly in women.

A number of studies have also indicated that during the spring and summer months, the body produces more seretonin (the so-called ‘feel good neurotransmitter’) because increased luminosity of sunlight. During the winter months as the amount of sunlight decreases, the body produces more melatonin, and this appears to inhibit sex drives. However, there is wide individual variation and the weather and subsequent hormone stimulation differs highly from one person to the next. As an online article by Shiv Joshi confirms:

“Sunlight has a direct effect on the brain’s serotonin production, according to researchers at the Human Neurotransmitter Laboratory and Alfred and Baker Medical Unit, Baker Heart Research Institute, Australia. Our serotonin levels increase with increase in luminosity. And how does that matter? Among other things, serotonin also regulates arousal, says Ray Sahelian, MD, author of Mind Boosters…Not just serotonin, but sunlight affects many other hormones in our body as well, some of which are associated with mood and pleasure feelings, according to professor Carmen Fusco, an instructor in pharmacology. It decreases melatonin, norepinephrine, and acetylcholine and increases cortisol, serotonin, GABA, and dopamine. The summer heat is good for your sex life too. It works on your muscles, by relaxing them and intensifies sensations of the skin. Further, the heat slows us down. This helps us get in touch with our more subdued sensual side, according to psychologist Stella Resnick, PhD, author of The Pleasure Zone”.

German researchers Winfried März and colleagues examined the relationship between vitamin D production (aided by sunny weather) and sex hormones (published a 2010 issue of the journal Clinical Endocrinology). In a study of 2,299 men, the researchers found that levels of Vitamin D were associated with androgen (i.e., testosterone) production with peak levels in August (the sunniest time of year in Germany). They concluded that testosterone and Vitamin D levels “are associated in men and reveal a concordant seasonal variation. Randomized controlled trials are warranted to evaluate the effect of vitamin D supplementation on androgen levels”. The study was replicated by Dr. Katharina Nimptsch and her colleagues among a sample of 1,362 men (also published in the same journal in 2012), and they found the same association between Vitamin D and testosterone production (although they found no seasonal effect). However, a more recent 2014 study published by Dr. Elizabeth Lerchbaim and her colleagues in the journal Andrology found no association (but it was on a much smaller sample of 225 men).

“Exposing the skin to sunlight for just 15-20 minutes can raise your testosterone levels by 120%, says a report from Boston State Hospital in the US. The research also found that the hormone increased by a whopping 200% when genital skin was exposed to the sun. Stick to the privacy of your own garden though – we don’t want any arrests”.

In previous blogs I briefly reviewed some of the many studies into courtship requests by Dr. Nicolas Guéguen (which you can read here and here). In one of his studies (published in a 2013 issue of Social Influence), Guéguen examined the effect of sunshine on romantic relationships (reasoning that sunny weather puts people in a better mood than non-sunny weather). In this study, an attractive 20-year old man approached young women walking alone in the street and asked them for their telephone number in two conditions (sunny or cloudy days). The temperature was controlled for and all days of the experiment were dry. The results showed that more women gave the man their telephone numbers on the sunny days. Guéguen concluded that positive mood induction by the sun may explain the success in courtship solicitation.

Finally, in his 2009 book Forensic and Medico-legal Aspects of Sexual Crimes and Unusual Sexual Practices, Dr. Aggrawal was quoted as saying that “like allergies, sexual arousal may occur from anything under the sun including the sun”. In fact, Aggrawal’s book arguably contains the most references to fetishes that concern the weather. This includes fetishes and paraphilias in relation to sexual arousal to sunny weather (actirasty), sexual arousal from the cold or winter (cheimaphilia), sexual arousal from snow (chionophilia), sexual arousal from thunderstorms (brontophilia), sexual arousal from thunder and lightning (keraunophilia), sexual arousal from fog (nebulophilia), sexual arousal from rain and being rained upon (ombrophilia and pluviophilia), and love of thunder (tonitrophilia). However, as far as I am aware, no scientific research has ever investigated any of these alleged fetishes.